Fix long-standing excessive file merges
Since switching to the multihead approach, we've been creating
excessive file-level merges where files are marked as merged with
their ancestors.
This explicitly checks at commit time whether the two parent versions
are linearly related, and if so, reduces the file check-in to a
non-merge. Then the file is compared against the remaining parent,
and, if equal, skips check-in of that file (as it's not changed).
Since we're not checking in all files that were different between
versions, we no longer need to mark so many files for merge. This
removes most of the 'm' state marking as well.
Finally, it is possible to do a tree-level merge with no file-level
changes. This will happen if one user changes file A and another
changes file B. Thus, if we have have two parents, we allow commit to
proceed even if there are no file-level changes.
#!/bin/sh
cat <<'EOF' > merge
#!/bin/sh
echo merging for `basename $1`
EOF
chmod +x merge
mkdir t
cd t
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "0 0"
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "0 0"
hg update 0
echo This is file c1 > c
hg add c
hg commit -m "commit #2" -d "0 0"
echo This is file b1 > b
env HGMERGE=../merge hg update -m 1
# no merges expected
cd ..; /bin/rm -rf t
mkdir t
cd t
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "0 0"
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "0 0"
hg update 0
echo This is file c1 > c
hg add c
hg commit -m "commit #2" -d "0 0"
echo This is file b2 > b
env HGMERGE=../merge hg update -m 1
# merge of b expected
cd ..; /bin/rm -rf t
mkdir t
cd t
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "0 0"
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "0 0"
echo This is file b22 > b
hg commit -m "commit #2" -d "0 0"
hg update 1
echo This is file c1 > c
hg add c
hg commit -m "commit #3" -d "0 0"
cat b
echo This is file b22 > b
env HGMERGE=../merge hg update -m 2
# merge expected!
cd ..; /bin/rm -rf t
mkdir t
cd t
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "0 0"
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "0 0"
echo This is file b22 > b
hg commit -m "commit #2" -d "0 0"
hg update 1
echo This is file c1 > c
hg add c
hg commit -m "commit #3" -d "0 0"
echo This is file b33 > b
env HGMERGE=../merge hg update -m 2
# merge of b expected
cd ..; /bin/rm -rf t